DETROIT — Thanks to Mike Napoli’s biceps and Koji Uehara’s filthy splitter, the Red Sox are nine innings away from the World Series.

The blue collar first baseman and the third arm to close for the club led the visitors to a 4-3 victory Thursday night over the Tigers in Game 5 of the ALCS in front of 42,669 at Comerica Park.

Napoli crushed a 460-foot homer to center field off Anibal Sanchez in the first, doubled and scored on a wild pitch in the third, singled in the fifth and dug several balls out of the dirt.

Uehara recorded the final five outs for his fourth save of the postseason and second of the ALCS.

With a 3-2 lead in the best-of-seven series that switches to Fenway Park for Game 6 Saturday and a possible Game 7 Sunday, the Red Sox will face Tigers gas-thrower Max Scherzer , with Justin Verlander in line for Game 7.

Still, Boston requires one victory to get to the World Series and the Tigers need two on the road against Clay Buchholz and John Lackey.

“Of course I want to get back there,’’ Napoli said of the World Series, which he played in for Texas in 2011. “But we can’t get too far ahead. We’re in good position, but we still have business to take care of.’’

Before Game 5, Tigers manager Jim Leyland said a loss would hurt his club more because the final two games will be played in New England’s living room, where the AL East champions won an AL-best 53 games.

“We have to win one game, that’s obvious,’’ Leyland said. “Win one game and take it from there.’’

Miguel Cabrera, battling lower half body woes, had a bad start to the game. Not only was he thrown out at the plate to end the first inning when third base coach Tom Brookens initially sent him home and then threw up a stop sign, Cabrera committed a fielding error in the second that led to an unearned run.

“He was waving him and probably stopped him a little late,’’ Leyland said of Brookens. “With Miggy right now, you have to stop him. It’s pretty rough right now.’’

Jon Lester wasn’t real sharp, but he posted the victory. In 5¹/₃ innings the lefty allowed two runs, seven hits and three walks.

Tigers catcher Alex Avila experienced a rough night. He was knocked over by David Ross in a plate collision, had a hard foul tip knock off his mask and left the game in the fourth with a strained left kneecap.

“The knee was pretty bad,’’ Leyland said.

After not allowing the Red Sox a hit or a run through six innings in Game 1, Sanchez gave up nine hits and four runs (three earned) in six innings.

The Tigers made it a 4-3 game in the seventh but traded two outs for the run. With Jose Iglesias on third and Torii Hunter on first with no outs, Junichi Tazawa got Cabrera to bounce into a 4-6-3 double play as Iglesias scored.

Brayan Pena’s one-out single to left-center off Tazawa in the sixth scored Victor Martinez and cut the Red Sox lead to 4-2. With runners on first and second, one out and Comerica loud, Tazawa fed Austin Jackson a 5-4-3 double play that choked the rally and quieted the crowd.

Uehara surfaced with one out in the eighth and retired five straight to deliver the Red Sox to the World Series doorstep.